Matthew is 3 times as old as Jenny. In 7 years, he will be twice as old as she will be then. How old is she now?
2 Answers
baxthum8 | High School Teacher | (Level 3) Associate Educator
Now: Let Jenny be "x", then Matthew is "3x".
In 7 years, Matthew will be 3x + 7, and Jenny is x + 7.
Matthew is twice as old as Jenny, therefore
`3x + 7 = 2(x + 7)`
`3x + 7 = 2x + 14`
`x + 7 = 14`
`x = 7`
Jenny is 7 years old now.
Check:
Now: Jenny is 7, which makes Matthew 21, 3 times as old.
In 7 years, Jenny will be 14 and Matthew will be 28, which is twice as old.
tonys538 | Student, Undergraduate | (Level 1) Valedictorian
Matthew is 3 times as old as Jenny. In 7 years, he will be twice as old as she will be then.
If Matthew is x years old now, Jenny's age is equal to x/3.
In 7 years, Matthew's age will be x + 7 and Jenny's age will be x/3 + 7
As Matthew would be twice as old as Jenny we get the equation:
x + 7 = 2*(x/3 + 7)
x + 7 = 2x/3 + 14
x/3 = 7
x = 21
Matthew's present age is 21 and Jenny is 7 years old now.